From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753364AbeCQO3y (ORCPT ); Sat, 17 Mar 2018 10:29:54 -0400 Received: from mail-wm0-f68.google.com ([74.125.82.68]:40827 "EHLO mail-wm0-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753315AbeCQO3w (ORCPT ); Sat, 17 Mar 2018 10:29:52 -0400 X-Google-Smtp-Source: AG47ELv33QcpFOr3Yk5Hovn+/1bTb7oziVy4F68sNfSbm8mqX/D10Y3pQzWh/jPK04Om3OJRpX9sbA== From: jason.vas.dias@gmail.com To: linux-kernel@vger.kernel.org Cc: x86@kernel.org, tglx@linutronix.de, mingo@kernel.org, peterz@infradead.org, andi@firstfloor.org Subject: [PATCH v4.16-rc5 1/2] x86/vdso: VDSO should handle clock_gettime(CLOCK_MONOTONIC_RAW) without syscall Date: Sat, 17 Mar 2018 14:29:33 +0000 Message-Id: <1521296974-12142-2-git-send-email-jason.vas.dias@gmail.com> X-Mailer: git-send-email 2.8.2 In-Reply-To: <1521296974-12142-1-git-send-email-jason.vas.dias@gmail.com> References: <1521296974-12142-1-git-send-email-jason.vas.dias@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This patch makes the vDSO handle clock_gettime(CLOCK_MONOTONIC_RAW,&ts) calls in the same way it handles clock_gettime(CLOCK_MONOTONIC,&ts) calls, reducing latency from @ 200-1000ns to @ 20ns. diff --git a/arch/x86/entry/vdso/vclock_gettime.c b/arch/x86/entry/vdso/vclock_gettime.c index f19856d..843b0a6 100644 --- a/arch/x86/entry/vdso/vclock_gettime.c +++ b/arch/x86/entry/vdso/vclock_gettime.c @@ -182,27 +182,49 @@ notrace static u64 vread_tsc(void) return last; } -notrace static inline u64 vgetsns(int *mode) +notrace static inline __always_inline u64 vgetcycles(int *mode) { - u64 v; - cycles_t cycles; - - if (gtod->vclock_mode == VCLOCK_TSC) - cycles = vread_tsc(); + switch (gtod->vclock_mode) { + case VCLOCK_TSC: + return vread_tsc(); #ifdef CONFIG_PARAVIRT_CLOCK - else if (gtod->vclock_mode == VCLOCK_PVCLOCK) - cycles = vread_pvclock(mode); + case VCLOCK_PVCLOCK: + return vread_pvclock(mode); #endif #ifdef CONFIG_HYPERV_TSCPAGE - else if (gtod->vclock_mode == VCLOCK_HVCLOCK) - cycles = vread_hvclock(mode); + case VCLOCK_HVCLOCK: + return vread_hvclock(mode); #endif - else + default: + break; + } + return 0; +} + +notrace static inline u64 vgetsns(int *mode) +{ + u64 v; + cycles_t cycles = vgetcycles(mode); + + if (cycles == 0) return 0; + v = (cycles - gtod->cycle_last) & gtod->mask; return v * gtod->mult; } +notrace static inline u64 vgetsns_raw(int *mode) +{ + u64 v; + cycles_t cycles = vgetcycles(mode); + + if (cycles == 0) + return 0; + + v = (cycles - gtod->cycle_last) & gtod->mask; + return v * gtod->raw_mult; +} + /* Code size doesn't matter (vdso is 4k anyway) and this is faster. */ notrace static int __always_inline do_realtime(struct timespec *ts) { @@ -246,6 +268,27 @@ notrace static int __always_inline do_monotonic(struct timespec *ts) return mode; } +notrace static __always_inline int do_monotonic_raw(struct timespec *ts) +{ + unsigned long seq; + u64 ns; + int mode; + + do { + seq = gtod_read_begin(gtod); + mode = gtod->vclock_mode; + ts->tv_sec = gtod->monotonic_time_raw_sec; + ns = gtod->monotonic_time_raw_nsec; + ns += vgetsns_raw(&mode); + ns >>= gtod->raw_shift; + } while (unlikely(gtod_read_retry(gtod, seq))); + + ts->tv_sec += __iter_div_u64_rem(ns, NSEC_PER_SEC, &ns); + ts->tv_nsec = ns; + + return mode; +} + notrace static void do_realtime_coarse(struct timespec *ts) { unsigned long seq; @@ -277,6 +320,10 @@ notrace int __vdso_clock_gettime(clockid_t clock, struct timespec *ts) if (do_monotonic(ts) == VCLOCK_NONE) goto fallback; break; + case CLOCK_MONOTONIC_RAW: + if (do_monotonic_raw(ts) == VCLOCK_NONE) + goto fallback; + break; case CLOCK_REALTIME_COARSE: do_realtime_coarse(ts); break; diff --git a/arch/x86/entry/vsyscall/vsyscall_gtod.c b/arch/x86/entry/vsyscall/vsyscall_gtod.c index e1216dd..c4d89b6 100644 --- a/arch/x86/entry/vsyscall/vsyscall_gtod.c +++ b/arch/x86/entry/vsyscall/vsyscall_gtod.c @@ -44,6 +44,8 @@ void update_vsyscall(struct timekeeper *tk) vdata->mask = tk->tkr_mono.mask; vdata->mult = tk->tkr_mono.mult; vdata->shift = tk->tkr_mono.shift; + vdata->raw_mult = tk->tkr_raw.mult; + vdata->raw_shift = tk->tkr_raw.shift; vdata->wall_time_sec = tk->xtime_sec; vdata->wall_time_snsec = tk->tkr_mono.xtime_nsec; @@ -74,5 +76,8 @@ void update_vsyscall(struct timekeeper *tk) vdata->monotonic_time_coarse_sec++; } + vdata->monotonic_time_raw_sec = tk->raw_sec; + vdata->monotonic_time_raw_nsec = tk->tkr_raw.xtime_nsec; + gtod_write_end(vdata); } diff --git a/arch/x86/include/asm/vgtod.h b/arch/x86/include/asm/vgtod.h index fb856c9..ec1a37c 100644 --- a/arch/x86/include/asm/vgtod.h +++ b/arch/x86/include/asm/vgtod.h @@ -22,7 +22,8 @@ struct vsyscall_gtod_data { u64 mask; u32 mult; u32 shift; - + u32 raw_mult; + u32 raw_shift; /* open coded 'struct timespec' */ u64 wall_time_snsec; gtod_long_t wall_time_sec; @@ -32,6 +33,8 @@ struct vsyscall_gtod_data { gtod_long_t wall_time_coarse_nsec; gtod_long_t monotonic_time_coarse_sec; gtod_long_t monotonic_time_coarse_nsec; + gtod_long_t monotonic_time_raw_sec; + gtod_long_t monotonic_time_raw_nsec; int tz_minuteswest; int tz_dsttime;